1. Field of the Invention
The present invention relates to a method of preventing the breakage of a webs in a rotary press used for multi-web printing which might lead to the breakage of another web.
2. Description of the Prior Art
In a conventional rotary press used for multi-web printing illustrated in FIG. 2, a web 2 in each unit mounted on a plurality of reel stands 1 is run to a printing unit and is printed on both sides thereof in a single color. The printed web is then guided by a group of guide rollers 4 to intermediate drag rollers 5 and is then slit into two strips each being half the width of the original one. After being slit, each of the webs is guided again by a group of guide rollers 4 to a triangular former drag roller 6 and, together with other webs which have been run from the other units, is pressed by a triangular former drag pressing roller 7 and then conveyed to a triangular former 8, before the web is sent out of the press through nipping rollers 9.
In a normal operation of multi-web printing, web breakage sensors 10 are provided at various sections in each unit for sensing web breakage at each section. When any one of the running webs is broken at any of these sections, one of the sensors 10 senses the breakage of the web and sends a signal to a controller (not shown) to stop all the units in the rotary press.
The rotary press shown in FIG. 2, is arranged such that when any one of a plurality of running webs 2 is broken, all the units are stopped. It often happens that breakage of a web causes another web 2 to be broken before all the units are stopped.